1. Field of the Invention
The present invention relates to data storage systems, and more particularly data patterns in data storage systems. Still more particularly, the present invention relates to a method and system for utilizing circular marks in position error signal patterns.
2. Description of the Prior Art
Designers, manufacturers, and users of computing systems require reliable and efficient digital information storage and retrieval equipment. Conventional data storage devices, such as magnetic disk drive storage systems, are typically used and are well known in the art. As the amount of information that is stored digitally increases, however, users of magnetic recording media need to be able to store larger and larger amounts of data in the recording media. To meet this demand, designers of magnetic recording media are working to reduce the size of the features on a storage disk.
One technique used to create smaller format patterns is proximity recording. Proximity recording is determined by the proximity of the recording head to the storage media, with magnetic recording being one example of proximity recording. Typically, marks formed by proximity recording can be located closer to each other than they can with far field recording. This is due to the fact that the width of the write head determines the width of the marks. And future magnetic write heads may reach dimensions as small as one hundred nanometers long by forty nanometers wide.
In conventional data storage systems, such as hard disk drives, write heads are rectangular shaped, which results in marks that are similarly shaped. Magnetic marks are best written with straight, radial edges because it makes it easier for the head to read the bits. But it is difficult to write rectangular marks close together due to the fringe fields created by a write head. When a write head is writing marks on one track, the fringe fields can partially erase the marks stored on adjacent track. This can cause the written rectangular marks to have curved ends, and curved ends make it more difficult to read the magnetic marks.
The present invention overcomes the limitations of the prior art by providing a method and system for using marks with curved edges in data patterns such as position error signal patterns, and sensing these marks with proximity recording heads. Circular, elliptical, and oval marks are examples of marks with curved edges that can be used in the present invention. The marks with curved edges are used to define data patterns (e.g. position error signal patterns) as a function of radius. If the marks with curved edges have been recorded longitudinally, an amplitude of a read back signal, such as a peak amplitude, is determined in order to generate a position error signal. If the marks with curved edges have been recorded vertically, an area under the curve of the read back signal is determined in order to generate a position error signal.